1. Technical Field of the Invention
The present invention relates to novel silane, siloxane or polysiloxane derivatives of merocyanine sulfones and to their formulation into cosmetics as “long” UV-A filters.
The present invention also relates to cosmetic compositions for topical application, in particular useful for the photoprotection of skin and/or hair, comprising an effective quantity of at least one silane, siloxane or polysiloxane derivative of merocyanine sulfone or a mixture of such derivatives.
2. Description of Background and/or Related and/or Prior Art
Radiation with wavelengths in the range 280 nm [nanometer] to 400 nm is known to brown human skin, and radiation with wavelengths in the range 280 nm to 320 nm, known as UV-B radiation, causes erythemas and burns to the skin which can interfere with the development of a natural tan.
UV-A radiation with wavelengths in the range 320 nm to 400 nm is also known to cause the skin to brown, but is capable of inducing an alteration in the skin, in particular in the case of sensitive skin and/or skin continuously exposed to solar radiation. In particular, UV-A radiation causes loss of skin elasticity and the appearance of wrinkles, resulting in premature aging of the skin. It promotes triggering of the erythematous reaction or amplifies that reaction in certain individuals and may even be at the source of phototoxic or photoallergic reactions. Thus, for aesthetic and cosmetic reasons, such as preserving the natural elasticity of the skin, more and more individuals wish to control the effect of UV-A radiation on their skin. The term “sun protection factor” means the ratio of the irradiation period necessary to reach the erythematogenic threshold in the presence of a test filter to the irradiation period necessary to reach that same threshold in the absence of a filter.
A large number of organic compounds suited to protect the skin against UV-A and/or UV-B radiation have been proposed to this art.
The majority of these are aromatic compounds absorbing UV radiation in the range 280 nm to 315 nm or in the range 315 nm to 400 nm and beyond, or across both of those zones. They are usually formulated into sunscreen compositions which are in the form of oil-in-water emulsions or water-in-oil emulsions. The organic filters, which are generally lipophilic or hydrophilic, are present in a dissolved state in one or the other of those phases in quantities appropriate for obtaining the desired sun protection factor (SPF).
In addition to their solar radiation filtration capability, desirable photoprotective compounds must also have other good cosmetic properties, good solubility in the usual solvents, in particular in fatty substances such as oils or fats, and good resistance to water and perspiration (persistance), as well as very good photostability.
Compounds which have been recommended for that purpose which are exemplary include a particularly interesting family of filters constituted by carbonaceous merocyanine derivatives described in U.S. Pat. No. 4,195,999 or WO-A-2004/006878. Those compounds have very good long UV-A filtering properties but have poor solubility in the usual organic solvents and in particular in fatty substances such as oils, and unsatisfactory photostability for certain merocyanine families.